1. Field of the Invention
The present invention relates to automotive evaporation combustion heaters and, more particularly, to automotive evaporation combustion heaters for vehicles, which are suitable as automotive cooling water heaters and room heaters.
2. Prior Art
Heaters using liquid fuel are used as heat sources permitting the engine to start in short period of time in winter seasons or as auxiliary heat sources for room heating of running cars. Also, these heaters are used as room heaters of electric cars because of the demand for power consumption reduction of these cars due to battery capacity restrictions.
FIG. 9 shows a prior art automotive heater of the pertaining type. In this automotive evaporation combustion heater, fuel is supplied by a fuel pump (not shown) from a fuel tank via a fuel pipe 20 to the vicinity of an ignition plug 3. Space surrounding the ignition plug 3 is communicated with an outer pipe 30 forming a combustion chamber. Fuel flows from space surrounding the ignition plug 3 into the outer pipe 30. The outer pipe 30 has a fuel evaporating medium 4 applied to its inner surface. The fuel evaporating medium 4 is made of ceramic wool or the like, and has numerous inner pores communicated with one another. Liquid fuel is retained in the fuel evaporating medium 4 by the capillary phenomenon.
In the outer pipe 30, an inner pipe 31 is coaxially disposed. Air for combustion is supplied by the air supply blower 16 into the inner pipe 31. A flame-retaining plate 32 is secured to an end of the inner pipe 31. A gap is formed between the end of the inner pipe 31 and the flame-retaining plate 32. The inner pipe 31 also has a number of axial slits. The outer and inner pipes 30 and 31 forms an annular combustion chamber between them. In this combustion chamber, fuel evaporated from the fuel evaporating medium 4 and air issued through the gap between the inner pipe 31 and the flame-retaining plate 32 and also through the slits of the inner pipe 31 are mixed and combusted.
Fuel is ignited by the ignition plug 3. The ignition plug 3 has a helical heat-generating element. When the heat-generating element is energized for a fixed period of time, it is heated hot to a high temperature and ignites vapor fuel evaporated from the liquid fuel.
The flame-retaining plate 32 also serves as a baffle plate for the annular combustion chamber, and promotes complete combustion of fuel. Furthermore, the flame-retaining plate 32 functions to prevent extinguishment of flame. Combustion gas is led from the combustion chamber through an orifice 29 therein, and flows as a combustion gas stream 33 from the inner side of the combustion cylinder 1 along the outer side of the combustion cylinder 1 to be exhausted through a combustion gas exhaust pipe 13.
Heat radiated from the combustion gas heats water circulated in the automotive evaporation combustion heater. The water is circulated by a pump between a heat exchanger (not shown) for generating hot air and the automotive evaporation combustion heater. Water pumped out for the pump is led through a cooling water lead pipe 14 and enters a space defined between an outer and an inner water guide pipes 34 and 35. The water entering the space is guided by a helical partitioning member 36 along the periphery of the inner water guide pipe 35, and is led out through a cooling water outlet pipe 15. The heat of the combustion gas heats water via the inner water guide pipe 35, and the heated water heats air in the heat exchanger. The heated air is supplied into and warms the car room.
A thermostat 37 and temperature fuses 38 are provided on the outer side of the automotive evaporation combustion heater, and are connected in series. In the event of abnormal heating of the automotive evaporation combustion heater due to such cause as idle heating, either of the thermostat 7 and temperature fuses 38 becomes non-conductive. When a controller detects this, it stops the fuel pump to interrupt fuel supply.
In the above prior art automotive evaporation combustion heater, however, the fuel evaporating medium 4 which is applied to the entire inner surface of the outer pipe 30, is voluminous. This means that long time is required from the ignition until steady combustion sets in with the heating by the fuel evaporating medium 4. Therefore, long rise time of combustion is required until the room warming effect is obtained.
Another problem in the prior art automotive evaporation combustion heater arises from the fact that usually only a single orifice 29 is provided. With the single orifice 29, the combustion cylinder 1 should have a large length for obtaining complete combustion of fuel. Besides, the heat exchanger for heating water transmits heat only from the outer surface of the inner water guide pipe 35. Therefore, the inner water guide pipe 35 should also have a large length for ensuring sufficient heat exchange effect. These requirements leads to a large heater size, imposing restriction on the heater installation place or dictating sacrifice in safety for determining the installation place when the heater is installed in the narrow engine room.
The present invention was made in view of the above problems, and it has an object of providing an automotive evaporation combustion heater, which permits reducing the rise time from the ignition till the rising of combustion provides the steady state of combustion.
Another object of the present invention is to provide an automative evaporation combustion heater, which is small in size and permits increasing the heat exchange efficiency.